Add the SPS chip

[BeboKhouja]

This PR adds the SPS chip, used for synchronization of the clock. It can make delta timing possible.

It has 2 outputs, with each being 16 bit, the first one is SPCT, or steps per clock tick. The second one is SPS, it returns the current average SPS, and should be close to the current SPS in the preferences. There are also 2 extra pins, which are SPS_OVERFLOW, and SPCT_OVERFLOW.